Managing views

This section describes how to manage views. Some sections are visible for specific types of the view like Union view or Join view.

Summary

This screen represents the summary information about the view. All the parameters are read only.

Parameter

Description

View name

Specifies the view name.

Full view name

Specifies the full view name with the database and schema name.

Row count

Number of the rows in the table.

Comment

The comment text.

Query rewrite target

Was the rewriting the queries enabled.

SQL text

The view SQL.

Available actions:

  • EDIT - goes to the editing view wizard where you cannot change the Schema and View type. The other options are the same as in the Adding a view section but are filled with already existing data. The only difference is that user can change the owner of the view to himself, by using Take ownership button.

  • DELETE - goes to the delete screen view.

Summary

Delete view summary

This screen presents a short summary of a view that you want to delete. The following read only details of the view section are presented on the screen: Virtual table name, Filter, SQL text. In addition, there are two tables presented.

Tale for Columns:

Column name

Description

Virtual column name

Name of the virtual column.

Virtual data type

Type of the virtual column with the nullability information.

Source column name

Name of the source column.

Source data type

Type of the source column with the nullability information.

Table for Calculated columns:

Column name

Description

Virtual column name

Name of the virtual column.

Virtual data type

Type of the virtual column with the nullability information.

Available actions:

  • CANCEL - cancels the delete operation.

  • DELETE - permanently removes the current view.

Remove

Preview data

In this screen, you can preview the data from the view. You can select the Limit of returning rows. The default value is 100, but you can select among a number of rows:

  • 10

  • 100

  • 1000

Available actions:

  • SHOW DATA - runs the query and shows the results on the screen.

  • CANCEL - cancels the running query.

Preview data

Columns

This screen presents the columns that are an output of the view. When the list of existing columns is loaded, you can directly click on the row to go to the details. Typing the text into the search box immediately looks for any presence of the search phrase in the Virtual column Name table column. The found phrase is marked yellow on matching elements.

Column name

Description

#

The column number.

Virtual column name

Name of the virtual column.

Virtual data type

Type of the virtual column with the nullability information.

Columns

Column details

It presents the selected column attributes: Virtual column name and Virtual column type.

Column details

Access rights

Please go to the Access rights section for general information about access rights. View access rights are listed below:

Access right

Description

Select

Confers to the grantee the ability to select the data.

Update

Confers to the grantee the ability to update the data.

View definition

Enables the grantee to access column metadata.

Tags

Please refer to the Tags section.

Union view

This section appears only when the created view was the type of Union view.

Union view

Join view

This section appears only when the created view was the type of Join view.

Join view

Dependency graph

This section allows to easily trace source data objects for this view.

Dependency graph

The view itself is shown at the top. Clicking the bar expands the list of columns. Clicking a column highlights all source columns in other objects.

Dependent views

When selecting this section, a list of all views that depend on this object appears. Clicking one of them opens the Dependency graph screen, with the object being high-lightened.

Dependent views

Clicking the bar expands the list of columns. Clicking a column highlights all source columns in other objects.

Primary and Foreign keys

Please refer to the Primary and Foreign Keys chapter of the manual.

Access rights

Please go to the Access rights section for general information about access rights. View access rights are listed below:

Access right

Description

Alter

Confers to the grantee the ability to alter the view.

Alter view

Confers to the grantee the ability to change view attributes.

Control

Confers to the grantee the ability to view definition and control database access rights.

Control view

Confers to the grantee the ability to view definition, alter, control view and create view access rights.

Delete

Confers to the grantee the ability to delete the data.

Insert

Confers to the grantee the ability to insert the data.

Select

Confers to the grantee the ability to select the data.

Update

Confers to the grantee the ability to update the data.

View definition

Enables the grantee to access database metadata.

Statistics

Shows the statistics for the view. This screen starts in read only mode. When you want to adjust the statistics manually please click EDIT button. On the screen, you can see the Use approximate distinct count option to improve the performance of statistics calculations with negligible deviation from the exact result, used if supported by the underlying engine. View row count shows how many rows are present in the view. For each column, you can examine the statistics in the following table:

Column name

Description

Column name

The virtual column name.

Distinct count

The number of the distinct values in the virtual column.

Average length bytes

The average length of columns where the bytes length can be calculated, for instance, character columns.

Calculate statistics

Specifies if the calculation of the column statistics should be performed and how.

To refresh the statistics you can use the Management tasks section.

Statistics

Available actions:

  • EDIT - goes to the edit mode screen.

Edit statistics

This screen allows you to modify statistics related values. It is the same screen as described above, but with editing capabilities.

Statistics edit

The Statistics calculation options are:

  • None

  • Shallow

  • Deep

Shallow statistics calculation does not propagate to the system holding the physical object. For example, let’s assume that the cached view resides in Apache Spark. With statistics calculated in Shallow mode, only Querona knows the results of the calculation and uses it for query optimization. Statistics of the physical table stored on Spark are not updated, potentially resulting in suboptimal queries. Deep mode orders the underlying system to update its statistics too thus allowing the system to prepare a better query plan.

Materialization

Please refer to the Materialization section.

Materialization of data

Management tasks

Please refer to the Management Tasks section.

Tags

Please refer to the Tags section.